It’s accepted as a truism that we live in a sex-drenched culture. From our pop- and reality-TV stars to our ready access to porn, the suggestion is that, when we’re not working, sleeping or feeding ourselves, we’re banging, thinking about banging, or watching videos of other people banging.

Yet the authors of “Don’t Put That in There” — both pediatricians and health researchers — dispute this with some cold-shower statistics.

For instance, despite the widespread belief that young people are hooking up with reckless abandon, Dr. Aaron E. Carroll and Dr. Rachel C. Vreeman found that about 57 percent of men and 51 percent of women ages 18 to 24 “have not had sex in the last year,” and that “only 36% of men reported having watched at least one pornographic film in the last year,” a finding consistent with other studies.

Here are some other sex myths that the authors debunk.

How big is big?

While the size of the average penis is often cited as 6 or, say the authors, 7 inches, these figures are more conjecture (and, for some, wishful thinking) than science.

One study of 2,545 men on the Internet found that the average penile length, erect, was “6.4 inches, with a standard deviation of 1.2 inches.”

A study of 1,661 American men by the Kinsey Institute set the average as 5.6 inches, and included the finding that “the average size was different based on how the man got the erection,” with those who were made erect by oral sex having longer lengths than those who were measured after manual stimulation.

But in both of these studies, the men measured themselves. More objective, presumably, were studies done by urologists. Rather than measure penises erect, they would “take a soft penis, stretch it out,” and measure from there, which is considered a “good substitute for measuring the erect penis.”

Of 15 studies performed this way, most “had averages in the range of 4.7 to 5.1 inches” — which, say the authors, gives us our true answer.

No sex before the big game

Athletes in certain big match scenarios, like Olympians or boxers, have long been told to curtail sexual activity the night before, or sometimes even weeks before, a big game.

Turns out their abstinence was not only wasted, but potentially harmful to their sporting efforts, as studies show that “the science of what happens in the body during and after sex suggests that … you might actually perform better if you have sex!”

In terms of the amount of energy expended, sex is a far less strenuous activity than some perceive — equivalent, they say, to simply walking up two flights of stairs.

“Estimates of how many calories are used up during sex range from 25 to 125,” they write. “That is not a lot of energy — especially for an athlete. Sex is only considered a mild to moderate intensity activity.”

What’s more, sex can increase testosterone, leading to better, not worse, performance the next day.

While the authors do note that “psychological or emotional” effects should not be discounted — sex that serves as an emotional distraction can render all these other points moot — sex as both testosterone-booster and mood-relaxer can serve as an enhancer for those going for the gold.

“If you sleep or relax better after sex,” they write, “then sex might be exactly what you need before your big competition.”

Can oysters make you horny?

Oysters are just one of the foods that have been reported over the years to increase sexual desire.

Casanova, the legendary lover, “was rumored to eat 50 oysters every morning to fuel his crazy sexual escapades,” and the Romans were documenting its randy effect on women as far back as the second century AD.

But is this effect real, or merely the result of some massive, self-perpetuating delusion?

The authors say that it’s likely the latter.

“No study has ever showed any sexually enhancing effect from oysters,” the authors write. “Nor can scientists find any special ingredient in the oyster that would suggest an ability to turn men or women into raging beasts. Oysters are mostly water, a few carbohydrates, and some minerals.”

Some have speculated that the oyster’s reputation results from its salty, liquid texture, which, when combined with its curved shell, could recall the female anatomy.

Researcher Alfred Kinsey was a pioneer in exploring American sexuality.Getty Images

Do marriage and masturbation mix?

Do married people masturbate less?

The assumption would be that ready access to a sexual partner renders self-service less necessary, but it’s disproven by science.

“One [study] found that people living with a sexual partner masturbated more,” the authors write, noting that “about 85% of such men and 45% of such women had masturbated in the last year” — compared to a separate study which found that “about 60% of men and 40% of women” overall, including those married and single, had done the same in that time period.

Do stinky guys repel women?

Conventional wisdom says that for men seeking a mate, or even just a hook-up, showering is No. 1 on the list of advisable pre-game behaviors.

Science surprisingly says the opposite.

Researchers at the University of California, Berkeley, studied the effect of male sweat on women by having groups of women “smell various compounds, one of which was androstadienone, a component of male sweat. They had them take twenty sniffs … over a two-hour time period.”

What they found was that “women who smelled the androstadienone had an improved mood and reported more sexual arousal. Those women also saw their blood pressure increase, their heart rates go up, and their breathing become more rapid.”

Some women may be unhappy with encouraging men to skip the shower after a vigorous workout — but hey, that’s science for you.

“The next time you men have worked up a sweat, and are considering a shower before engaging that woman you’re interested in,” the authors write, “you may want to reconsider. That sweat may do more to help your case than hurt it.”

To cut, or not?

Circumcision is a controversial topic. Driven as it is by a mix of religious and sociological factors, it is perceived as medically and sexually wise by some, and as risky barbarism by others.

Recent studies, the authors write, have shed much-needed light on what circumcision means for men. First, “male circumcision protects against several diseases,” lessening a male’s odds of contracting “urinary tract infections, herpes, syphilis, chancroid, and invasive cancer of the penis.”

Also, “men who have been circumcised are actually 50% to 60% less likely to get HIV.”

ShutterstockBut circumcision is not only valuable for male health, as woman who have sex with circumcised partners are less likely to catch the sexually transmitted infections Trichomonas and bacterial vaginosis.

Those who oppose circumcision cite risks, and “like any surgical procedure,” these can be valid, as infections or worse are possible. But the authors cite studies showing that complication rates are very low — for babies, just 0.2 to 0.4 percent.

One of the other reasons often cited for opposing circumcision — decreased penile sensitivity in circumcised men — is not borne out by science.

As researchers studied whether circumcision helped prevent the spread of HIV, they were able to conduct far better studies than before on penile sensitivity.

One inquiry included thousands of Kenyan men who were split into two random groups, only one of which would have its participants circumcised.

With a large sample of previously uncircumcised men now willing to be circumsized for the study, scientists finally had a basis for comparing sensitivities with regard to circumcision, and their findings belied the conventional wisdom.

“Overall, the circumcised men actually report that their penises are more sensitive [after circumcision], and that they have an easier time reaching orgasm,” the authors wrote.

Further, in a collective review of 10 studies using almost 20,000 men as subjects, scientists “did not see any differences between circumcised and uncircumcised men in terms of sexual desire, pain during sex, premature ejaculation, problems with erections, or problems with orgasms.”

Getty Images

Does the G-spot exist?

The G-spot is “an especially sensitive zone that supposedly exists in a woman’s vagina,” leading to greater intensity of pleasure during sex.

While many women would surely weigh in strongly on this matter — “in multiple large surveys,” the authors write, “a majority of women report that they have G-spots” — for science, the question of the G-spot’s existence inspires passionate debate.

“Surprisingly enough, scientists, gynecologists, and sex researchers argue about this all the time,” write the authors. “The opinions disagree so strongly that you could imagine these researchers getting into fist fights over the issue.”

The problem is, while many women experience a certain spot that increases their sexual pleasure, science has had trouble pinpointing the particulars, an effort made more difficult by the observation that it seems to manifest differently in some women, with others appearing not to have it at all.

The G-spot, according to scientists who believe, is “located on the front wall of the vagina, about halfway between the pubic bone and the cervix.”

In a 1982 book that gave the spot its name, Drs. John Perry and Beverly Whipple attributed the sensitivity of the area to “a number of anatomical structures [that] come together there: blood vessels, glands and ducts on either side of the urethra, nerve endings, the vaginal wall, and the neck of the bladder.”

While many studies “support the existence of this area in terms of the various components coming together in one area … they also suggest that the composition of this area is somewhat different from one woman to the other,” which could explain differing reactions from women, as well as different perceptions by scientists.

Furthermore, it’s been shown via biopsies that “this potential G-spot area does not have more nerve endings than other parts of the vagina,” and through MRIs that the area lacks “an obvious structure.”

Overall, though, the authors report that “the science supposedly disproving the G-spot is not particularly strong,” and say that they come down on the side of its existence, citing the clear majority opinion of self-reporting — and, it would appear, extremely satisfied — women.

Big feet, big hands — big delusion

Do big hands and big feet signal another sizable appendage lurking nearby? Rumor has long held that if a man has large hands and feet, this was somehow indicative of a large penis as well.

What’s odd about this, though, is that this misplaced theory is not based solely on the obvious visuals, but on genetics as well, as a gene known as the Hox gene “plays a role in the development of the toes and fingers,” and also in the growth of “the penis and the clitoris.”

But when examined by science, “there is no good evidence that men with big feet have bigger penises.”

Studies, including “The Definitive Penis Size Survey,” in which “3,100 men reported information about the sizes of their penis and their other characteristics,” have shown no correlation between hand and foot size and penis size.